Aviation fuel blending agent and method for producing same



Jan. 27, 1953 M. R. MoRRow AVIATION FUEL BLENDING AGENT ANDl METHOD FOR PRODUCING SAME Filed March 28, 1949 Morris R. Morrow,

av m- En Patented Jen. 27, 1953 AJEATIN FUEL BLENBNG AGENT ANB METHD FR PRGDUJENG- SAME Morris R.. Morrow, Baytown, Tex., assigner, by

mesne assignments, to Standard il Development Company, Elisabeth, N. J., a corporation of Delaware Application March 28, 1949, Serial No. 83,979

(Si. ld-w73) 4.- Claims. l

The present invention is directed to a method for producing an aviation fuel blending agent. More particularly, the invention is directed to a method for forming a fraction comprising aromatic and paraiiinic hydrocarbons having enhanced anti-knock qualities.

Prior to the present invention it has been known that aromatic hydrocarbons have desirable characteristics which malte them suitable for inclusion in aviation fuels. It has also been known that aromatic hydrocarbons are very good solvents for employment in the paint and lacquer industry and in many other services where aromatic hydrocarbons iind usage. It has been customary prior to the present invention, in obtaining aromatic hydrocarbon fractions for employment in aviation fuels, to resort to expensive nrocedures to concentrate the aromatic hydrocarbons. Thus, for example, it has been known to subject selected hydrocarbon fractions containing nanhthenes to hydroforming conditions wherein the naphthenes are converted to the corresponding aromatics. The resulting product from the hydroforming operation is then subjected to distillation to recover fractiom having desirable boiling ranges which are then subjected. to solvent extraction to obtain aromatic hydrocarbons or concentrates which can be included in aviation gasolines. Such procedures are disadvantageous in that it is necessary to subject the aromatic containing hydrocarbon fractions to expensive solvent extraction procedures to recover a substantially puriiied product.

It is, therefore, the main object of :the present invention to prepare an aromatic fraction suitable for inclusion in aviation fuels without resort to solvent extraction.

Another object or the present invention is to provide a method for recovering a fraction including aromatics and para-inns which has substantially improved anti-knock qualities.

A still further object of the present invention is to prepare by distillation a fraction comprising paraflinic and aromatic hydrocarbons of improved octane number characteristics.

The objects of the present invention are obtained by forming a fraction consisting substantially of aromatic, paramic, naphthenic and olenic hydrocarbons boiling in the range between 200 and 253 E'. and distilling said fraction to obtain a fraction boiling in the range between 220 and 245 il'. The fraction boiling in the range between 220 and 245 F. has substantially improved octane number characteristics and its anti-knock qualities make it suitable for inclusion n aviation gasoline.

The present invention, therefore, may be described brieiiy as involving the formation of a hydrocarbon fraction boiling in the range between 200o and 250 E'. and containing substantially aromatic, paranic, naphthenic and olennic hydrocarbons. Such a fraction may be formed, for example, by hydroforming a fraction boiling in the range between 200 to 325 F. and containing aromatic, naphthenc and paramnic hydrocarbons and ir" desired, olenic hydrocarbons. iiydroforming is a well known technique and details of the hydroforming procedures may be found in U. S. 2,400,363 issued May 14, 1946, in the name of Herbert H. Meier. From the hydroforrned product a fraction boiling in the range between 200 and 250 F. may be separated, for example, by distillation, which has the desired characteristics as a feed stock for the process of the present invention. The fraction having the characteristics enumerated and containing substantially aromatic, parailinic, naphthenic and oleiinic hydrocarbons is subjected to a distillation operation in eicient fractionating equipment to separate a fraction boiling in the range between 220 and 245, Such a fraction has enhanced octane number or anti-knock qualities which ineke it suitable for inclusion in an aviation fuel. This fraction consists substantially of aromatcs and other hydrocarbons having good octane number characteristics.

The invention will be further illustrated by reference to the drawing in which the single figure is a flow diagram of a preferred mode of practicing my invention. Referring now to the drawing, numeral l l designates a charge line by which a fraction boiling in the range between 200 and 325 F. containing aromatics, naphthenes and paraiiins and if desired,l olerlns, is charged into hydroforming zone i2 which is indicated as a loci: in the diagram. It will be understood that hydroforming zone l2 will include a suitable catalyst such as that described in the aforesaid patent to Meier and that the conditions in the hydroforrning zone will be similar to the conditions given in the Meier patent supra. Zone I2 is provided with a line I3 through which hydrogen may be discharged therefrom. Conditions in zone l2 are adjusted to cause conversion of naphthenes to aromatics, the aromatics originally present in the feed stock and the parains being substantially inert to the reaction and passing through hydroforming zone l2 substantially unaffected. The product leaving hydroforming Zone i2 by line ifi is discharged thereby into a lirst distillation zone l5 which is provided respectively with lines Iii, l1, i8, I9, and 20. An

overhead fraction comprising butanes and lighter hydrocarbons is removed from distillation zone |5 by line I5, whereas pentanes and fractions boiling up to 200 F. are removed from Zone |5 by line for use as a gasoline blending agent or as desired. A fraction boiling in the range between 200 and 250 F. consisting substantially of aromatic, naphthenic, paralnic, and oleiinic hydrocarbons is withdrawn from zone l5 by line I8 and discharged into second distillation zone 2| wherein it is distilled in a manner which will be described. A fraction boiling in the range between 250 and 300 F. is withdrawn from zone |5 by line I9 and may be introduced into a solvent extraction zone such as one employing liqueed sulfur dioxide as a solvent at a low temperature in the range between 20 F. and 60 F. in order to recover the desired aromatics therefrom in a substantially purified condition. The heavier fractions may be Withdrawn by line and may find use in motor gasoline or as a cracking stock. It will be noted that distillation zone l5 is provided with a heating means 22 which is illustrated as an internal steam coil. It is also understood that distillation zone I5 is equipped with internal baffle equipment such as bell cap trays, packing and other means for insuring intimate contact between vapors and liquids in order to cause separation of the desirable fractions.

Distillation zone 2| is similar to distillation zone l5, but is operated under conditions conducive to more precise fractionation. Zone 2| is provided with a heating means illustrated by coil 23 for adjustment of temperature and pressure therein. Distillation zone 2|, like distillation zone I5, is provided with suitable internal equipment such as bell cap trays, packing and other means to insure intimate contact between vapors and liquids and to allow separation of the desirable fractions as will be described. Distillation zone 2| is also provided with lines 24, 25, and 26. After conditions have been adjusted properly in Zone 2| there is removed overhead therefrom by line 24 a fraction boiling in the range between 200 and 220 F. containing aromatics which may be routed to a solvent extraction zone not shown for separation of desirable aromatics therefrom. There is recovered from zone 2| by line 26 a fraction boiling in the range between 245 and 25 F. which may also be routed to a solvent extraction zone not shown for recovery of desirable aromatics therefrom. Line is provided whereby the deirable fraction boiling fn the range between 220 and 245 F. which comprises aviation fuel blending agent produced in the present invention. This fraction consists predominantly of aromatic and paraffinic hydrocarbons and has improved octane number characteristics. The concentration of aromatics in this fraction is between 60% and 80% by volume. By virtue of concentrating the aromatic, parainic, naphthenic and olenic fractions boiling in the range between 200 and 250 F., it is possible to distill therefrom a fraction boiling in the range between 220 and 245 F. which is eminently suitable as an aviation fuel blending agent.

The reason for the peculiar enhanced properties of the fuel boiling in the range between 220 and 245 F. produced by distillation of the 200- 250 fraction is not entirely understood and may not be predicted from the composition of the feed stock charged to hydroforming zone I2. This hydroformer feed ordinarily boils in the range between 200 and 325 F. and may comprise approximately 10% by volume aromatic hydrocarbons, 43% by volume naphthenic hydrocarbons, 47% by volume paraffinic hydrocarbons and a trace of olens. Neither is it predictable from the composition of the fraction obtained by line |8 from distillation zone |5 boiling in the range between 200 and 250 F. which may contain approximately 50% by volume aromatic hydrocarbons, 12% by volume naphthenic hydrocarbons, 35% by volume parafnic hydrocarbons and 3% by volume olefinic hydrocarbons.

In an effort to characterize the components present in the 200-250 F. boiling range fraction, a raffinate was examined, which had been produced from this fraction by solvent extraction With liquid sulfur dioxide at a low temperature of about -30 F. under conditions which allowed the recovery of aromatics from the mixture in substantially pure form. The ranate or non-aromatic portion of this fraction was then tested for antiknock characteristics. The Supercharge rich rating of the 220-245 portion of this raffinate with 4 cc. tetraethyl lead (T. E. L.) per gallon added thereto was 104 I. M. E. P. (This method of quality characterization is known as the Supercharge method for determining the knock characteristics of aviation fuels and is described in the A. S. T. M. Standards on Petroleum Products and Lubricants, Committee D2, 1938, Test D909-48T.) The rating of the same 220 to 245 F. boiling range fraction produced by distillation alone from the 200-250 F. boiling range hydroformate fraction was 242 I. M. E. P. This fraction contained approximately 60% toluene, and, therefore, it was possible to calculate the octane quality of the non-aromatic portion of this fraction by subtracting the eiect of the toluene (which was the only aromatic present) from the octane rating of the fraction. The value so calculated was 138 I. M. E. P., or approximately 34 points higher than the rating of the non-aromatic portion of the raffinate described heretofore. Octane ratings of this order of magnitude are not characteristic of components boiling in this range. To conrm this calculated rating of 138 I. M. E. P., a sample of the distillate 220-245 F. fraction containing 60% toluene was solvent extracted at about 90 F. with liquid sulfur dioxide to obtain great selectivity and thus remove substantially completely the aromatic portion of the distillate. The octane rating on the raffinate from this extraction was found to be in very good agreement with the value of 138 I. M. E. P. calculated as described above.

By adjusting the composition of the feed stock introduced by line into the hydroformer I2, it will be possible to produce aromatic concentrates of 220-245 F. boiling range containing more than 60% aromatics. As a further example, such a fraction containing approximately aromatics (toluene) shows a similar advantage for producing this fraction by distillation rather than reblending the solvent extracted products of the same boiling range since the I. M. E. P. reference number of the non-aromatic portion so distilled is 128 as compared with 104 mentioned previously. This advantage also was conrmed by employing extremely low temperature extraction as described heretofore.

It is indeed surprising thatI the fraction produced by distillation should have such enhanced octane characteristics over one produced by solvent extraction. It is obvious that the octane rating of the combined aromatic and non-aromatic components in the 220-245 F. boiling. range fraction produced in accordance with my invention is superior to that of a blend which could be made to the same aromatics concentration and boiling range from aromatics and nonaromatics produced by solvent extraction.

As mentioned previously, the reason for obtaining this surprising result is not entirely understood, but it is believed that the presence of aromatic hydrocarbons with the non-aromatic hydrocarbons boiling in the range between 200- 250 F. may result in the non-aromatic hydrocarbons of superior quality having abnormal behavior which allows them to be segregated by distillation with the aromatics.

In order to obtain the desirable results, as a general statement, it may be said that the aromatic and paralnic hydrocarbon content of the fraction boiling in the range between 200 and 250 F. should comprise a major amount of the fraction, while minor amounts of the fraction will comprise naphthenic and olenic hydrocarbons. Further, it may be stated that the aromatic hydrocarbons should be in excess of the paranic hydrocarbons and the naphthenic hydrocarbons should be present in lesser amounts than the parainic hydrocarbons and in greater amounts than the olenic hydrocarbons. Apparently, an excess of aromatic hydrocarbons over parainic hydrocarbons allows the latter to be distilled to obtain a fraction boiling in the range between 220 to 245 F. having the unusual octane number characteristics.

The nature and objects of the present invention having been completely described and illustrated, what I wish to claim as new and useful and to secure by Letters Patent is:

1. A method for obtaining an aviation fuel blending agent of improved anti-knock qualities which comprises forming a rst fraction boiling in the range between 200 and 250 F. and consisting substantially of a major amount of aromatic and parafnic hydrocarbons, said aromatic hydrocarbons being in excess of said paraflinic hydrocarbons, and minor amounts of naphthenic and olem'c hydrocarbons, said naphthenic hydrocarbons being in excess of said oleiinic hydrocarbons, and distilling said rst fraction under suitable conditions to obtain a second fraction boiling in the range between 220 and 245 F. having an I. M. E. P. of 242 and consisting of an amount of aromatic hydrocarbons in the range between 60% and 80% by volume and the remainder predominantly parafnic hydrocarbons, said remainder having an I. M. E. P. of at least 128 on addition thereto of 4 cc. of tetraethyl lead per gallon suitable for use in aviation fuels.

2. A method in accordance with claim 1 in which the rst fraction consists substantially of by volume aromatic hydrocarbons, 35% by Volume parafnic hydrocarbons, 12% by volume naphthenic hydrocarbons, and 3% by volume olenic hydrocarbons.

3. An aviation fuel blending agent boiling in the range between 220 and 245 F. consisting of aromatic hydrocarbons, in an amount in the range between and 80% by volume, and the remainder predominantly paraflinic hydrocarbons, said remainder having an I. M. E. P. of at least 128 on addition thereto of 4 c. c. of tetraethyl lead per gallon.

4. An aviation fuel blending agent boiling in in the range between 220 and 245 F. having an I. M. E. P. of 242 consisting of toluene in an amount in the range between 60% and 80% by volume and the remainder predominantly parafflnic hydrocarbons, said remainder having an I. M. E. P. of at least 128 on addition thereto of 4 cc. of tetraethyl lead per gallons.

MORRIS R. MORROW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,249,461 Diwoky July 15, 1941 2,401,983 Stanly et al June 11, 1946 2,404,902 Claussen et al. July 30, 1946 2,405,660 Linn Aug. 13, 1946 2,406,667 Clarke Aug. 27, 1946 2,408.724 Bailie et al. Oct. 8, 1946 2,429,718 Harding Oct. 28, 1947 

1. A METHOD FOR OBTAINING AN AVIATION FUEL BLENDING AGENT OF IMPROVED ANTI-KNOCK QUALITIES WHICH COMPRISES FORMING A FIRST FRACTION BOILING IN THE RANGE BETWEEN 200* AND 250* F. AND CONSISTING SUBSTANTIALLY OF A MAJOR AMOUNT OF AROMATIC AND PARAFFINIC HYDROCARBONS, SAID AROMATIC HYDROCARBONS BEING IN EXCESS OF SAID PARAFFINIC HYDROCARBONS, AND MINOR AMOUNTS OF NAPHTHENIC AND OLEFINIC HYDROCARBONS, SAID NAPHTHENIC HYDROCARBONS BEING IN EXCESS OF SAID OLEFINIC HYDROCARBONS, AND DISTILLING SAID FIRST FRACTION UNDER SUITABLE CONDITIONS TO OBTAIN A SECOND FRACTION BOILING IN THE RANGE BETWEEN 220* AND 245* F. HAVING AN I.M.E.P. OF 242 AND CONSISTING OF AN AMOUNT OF AROMATIC HYDROCARBONS IN THE RANGE BETWEEN 60% AND 80% BY VOLUME AND THE REMAINDER PREDOMINANTLY PARAFINIC HYDROCARBONS, SAID REMAINDER HAVING AN I.M.E.P. OF AT LEAST 128 ON ADDITION THERETO OF 4CC. OF TETRAETHYL LEAD PER GALLON SUITABLE FOR USE IN AVIATION FUELS. 